Produces a File mapper that pairs a descendant of oldBase with a file in newBase that preserving the relative path of the original file against oldBase.

Produces a File mapper that pairs a descendant of oldBase with a file in newBase that preserving the relative path of the original file against oldBase.
For example, if oldBase is /old/x/ and newBase is /new/a/, /old/x/y/z.txt gets paired with /new/a/y/z.txt.

A path mapper that pairs a descendent of oldBase with newBase prepended to the path relative to oldBase.

A path mapper that pairs a descendent of oldBase with newBase prepended to the path relative to oldBase.
For example, if oldBase = /old/x/ and newBase = new/a/, then /old/x/y/z.txt gets paired with new/a/y/z.txt.